Grazing Is Good For Butterflies

Here's an interesting example of how, once humans have altered the environment, continued human intervention -- in this case grazing -- can help to mitigate the impacts.

The Checkerspot Mystery: An Ecological Whodunit ... the nitrogen oxide emissions from cars commuting to Silicon Valley enriched the nutrient-poor serpentine-rock soil that sustains the native grasslands on Coyote Ridge. This soil enrichment allowed invasive grasses -- which flourish in more nitrogen-rich soil -- to out-compete the native plants on which the checkerspot [butterfly] depends. When local ranchers stopped grazing their cows on one side of the ridge, it made things worse, because grazing helped keep invasive grasses in check.